Unless you have really tall ceilings, pick a nice day and take the canoe outside. At this stage the hull is getting some strength, but you still need to be careful when moving it around. Lean it up against a wall or tree so that the stem is level with the ground. Tape off 1" of the open end of the stem with masking tape to make a dam, mix 3 oz. of a epoxy/low-density mixture to a molasses consistancy, and pour it into the stem. When it is partially cured top it with a slightly thicker microlight mixture so that the plug is about 1" thick.
When this plug is completely cured, turn the canoe over and repeat with the other stem. When they are sanded and primed they will look like this; not quite as pretty as a radiused fillet but a whole lot easier to do!
